The prevalent usage of Internet for information gathering and sharing, social networking, and commerce have given users reasons to demand new computation and communication hardware with more memories and faster processing rates. The advancement of semiconductor manufacturing has lowered the cost of manufacturing semiconductor chips and makes such new hardware affordable to the majority of people all over the world. Examples of hardware that utilize such new semiconductor chips include computers, personal digital assistants (PDAs), mobile phones, global positioning systems (GPSs), etc. Further, with the lowering of manufacturing costs of semiconductor chips, the usage of semiconductor chips are increasing expanded in other fields and applications. For example, more and more components of automobiles and home appliances include semiconductor chips as controllers, sensors, displays, etc. With the expanded applications, processing capabilities, and/or storage capacities, the demand for semiconductor chips has greatly increased. At the same time, the chip design and product cycles of semiconductor chips have both shortened to meet the demand of end users. Semiconductor manufacturers also need to respond to the shortened cycles to bring products to the market in a timely manner.
The manufacturing of semiconductor chips involves substrate processing to make devices and die packaging. Semiconductor substrate processing involves film deposition, lithographical patterning, dopant implant, etching, planarization, cleaning, etc. Some semiconductor chips require 50 lithographical layers or more to define and to connect devices. Therefore, the manufacturing of semiconductor chips from bare silicon substrates to assembled and tested chips can take 2-3 months. With instability in the global economy and consumers' interests, managing the inventory of semiconductor chips is very challenging. Overstocking of semiconductor chips very costly. On the other hand, shortage of stock (or stockout) can pose serious problems for customers. How to properly manage (or control) inventory to meet the demand is critical.